A photoreactive crystalline quasiracemateElectronic supplementary information (ESI) available: Detailed description of synthesis, 1H-NMR, and 13C-NMR analyses. CCDC 782795-782798. For ESI and crystallographic data in CIF or other electronic format see DOI: See DOI: 10.1039/c0cc02775h

Rationally designed racemic and quasiracemic sulfonamidecinnamic acids assemble to give hydrogen-bonded dimers with coplanar alignment of neighboring olefins. The quasiracemate phase contains near inversion-related motifs with chemically distinct components forming supramolecular heterodimers that undergo asymmetric photodimerization. A rationally designed quasiracemic sulfonamidecinnamic acid assembles to form hydrogen-bonded dimers that undergoes single-crystal-to-single-crystal enantioselective [2+2] photodimerization.